The present invention is in a surgical sponge or compress and a process for the manufacture thereof. The surgical sponge is made from a fleece consolidated by intertangling fibers or by fusion, from a majority of cellulosic fibers, with an X-ray contrast medium autogenously and irremovably fastened thereto, which consists of a polymeric synthetic matrix filled with a material impermeable to X-rays, into which at least some of the fleece fibers adjacent to it are embedded, and which contains absorbent material in amounts of at least 40 weight-percent.
After surgical intervention, it is necessary to make certain that every such sponge or compress is removed from the patient's body. It is therefore common practice to provide these materials with color identification that clearly distinguishes them from the color of blood, by using, for example, blue or green dyed filaments. The dyes can also be made reflective, phosphorescent, fluorescent or iridescent.
In spite of all precautions, however, it is not always possible to prevent sponge material from being accidentally left in the site of the operation. If a patient is having unusual post-operation discomfort, it must be determined whether the discomfort is caused by any overlooked sponge material. It is therefore necessary to provide surgical sponges at certain points with materials or embedments which are impermeable to X-rays, and which can be detected as shadows in the X-ray photograph in case of doubt, and thus permit positive detection. The X-ray impermeable material is generally barium sulfate in particle form.
EP-A No. 160,560 describes a surgical sponge of nonwoven material containing no binding agent and consolidated and perforated by high-pressure water jets, in whose interior at least one X-ray-absorbent element (X-ray contrast medium) is situated between the fiber layers as an integral component of the sponge.
This element is held in position by entangling fibers. The X-ray contrast medium preferably consists of at least one yarn, fiber ribbon or endless monofilament with a polymeric, thermoplastic matrix which contains barium sulfate embedded in amounts of approximately 60 weight-percent. The matrix is partially thermally bound to the surrounding nonwoven fibers, i.e., the fibers are embedded in the matrix softened afterward by hot compression, and thus they fix the monofilament or yarn in place.
The nonwovens can consist of natural or synthetic randomly laid fibers or mixtures thereof. The matrix of the X-ray contrast medium preferably consists of polyvinyl chloride in the case of monofilaments, has a diameter of about 0.6 mm, and in addition to the barium sulfate, contains pigments which are of a color that contrasts clearly with that of blood. In any case, however, it must have thermoplastic properties in order to be fused afterward to the surrounding fibers.
The arrangement of a number of X-ray contrast filaments in patterns or rows, and the number thereof, depends on the size and folding with which the sponge is to be used. It must only be assured that each sponge ready for use contains a sufficient number of contrast threads. Fragments of filaments can also be incorporated. Any sponge that might be erroneously left in the wound is distinguished by its patterned or interrupted arrangement from any suture material also containing contrast agents which must necessarily be left in the body.
DE-OS No. 26 00 185 discloses a process in which a surgical sponge is made with an insert intimately and permanently bonded to the fibers by extruding a melted filament of X-ray impermeable, thermoplastic material onto a moving, absorbent fabric, and pressed in the still tacky state against the fabric. A compressed strand is thus formed with surrounding fibers embedded therein. Subsequent remelting of the thermoplastic material is not necessary. No guide for the selection of appropriate thermoplastic polymers is given.
The known sponges have a number of product-related and also process-related disadvantages. For instance, the clarity of the contrast on the X-ray photograph depends on the amount of the applied contrast medium, the density (percentage content) of the X-ray contrast particles and the radiation dose. To minimize the exposure of the human body to radiation it is desirable to maintain the radiation dose as low as possible. It is also desirable to have the highest possible content of contrast agent in the polymer matrix, such as 60 weight-percent and more.
Inorganic particles, usually barium sulfate, incorporated into the matrix in the said amounts produce a drastic hardening and reduction of the flexibility in the thermoplastic matrix. The effect of the hardening is so pronounced that, for example, a contrast filament according to DE-OS No. 26 00 185 or with a PVC matrix according to EP-A No. 160 560 cannot be at all satisfactorily extruded (spun) unless the plasticizer content is unusually high. Consequently, those matrix materials which cannot be mixed with plasticizers or which are rendered inherently soft only by copolymerization must not be used in making X-ray contrast monofilaments with large proportions of barium sulfate filler.
Even the thermoplastics which can be treated with plasticizers which are essential to them have disadvantages in applications in surgical sponges since plasticizers diffuse, or migrate, within the nonwoven and therefore can have a toxic effect in contact with wounds.
In the interest of achieving more reliable detection, the above-cited applications propose the thermal fixation of X-ray contrast fibers which are relatively thick (0.64 mm) over their entire length, while or after they are deposited. Experience shows, however, that, there is a considerable impairment or even prevention of the (multiple) folding of the sponge due to the thickness of the filament. Mere spot-fixation, however, does not suffice to reliably fix the contrast filaments because filling the matrix with a large proportion of contrast agent considerably impairs its adhesiveness in the heat-softened state.
Gauze or nonwoven gauze substitutes are normally supplied unsterilized and are sterilized in hospital steam sterilizers by the pulsating pressure-vacuum principle at 134.degree. C. in the autoclave. Hot steam sterilization is possible, for example, with cotton-containing fabrics or nonwovens. However, there is a danger that the layered and folded pads may stick together after steam sterilization if the matrix of the X-ray contrast medium consists of thermoplastic polymers with added plasticized polymers.
An object of the present invention is to overcome the above described disadvantages by providing an improved surgical sponge, and a novel method of producing it. The polymer matrix of the contrast medium must therefore be free of plasticizers and yet soft, flexible and resilient, and must be capable of withstanding hot steam sterilization without softening. It must nevertheless be easily extrudable even with high contents of contrast agent. The fixation of the X-ray contrast medium in the still adhesive state directly after extrusion must be possible in an autogenous and permanent manner in or on the nonwoven material of the sponge, without impairing the ability of the sponge to be repeatedly folded.
The term, "X-ray contrast medium", as used herein will be understood to mean any kind of incorporation of a substance absorbing X-rays, usually barium sulfate, into the polymer matrix. The system can have any desired geometrical shape. Furthermore, it is desirable to distribute a relatively large number of contrast media in, or on, the nonwoven fabric in order to assure reliable detection with X-rays.